Various amine solutions have been used for the removal of acidic gases from gases and liquids. Common acidic gases may include, CO2, H2S, CS2, HCN, COS and oxygen and sulfur derivatives of C1 to C4 hydrocarbons. In general, the treatment of gases and liquids containing acidic gases, such as CO2 and H2S, with certain amine solutions typically results in the simultaneous removal of substantial amounts of both CO2 and H2S. However, in some instances, it may be desirable to treat acidic gas mixtures containing both CO2 and H2S so as to selectively remove H2S from the mixture, thereby minimizing removal of the CO2. Selective removal of H2S results in a relatively high H2S/CO2 ratio in the separated acid gas which may aid in the conversion of H2S to elemental sulfur using the Claus process.
Sterically hindered amines have been used for the selective removal of H2S from gaseous mixtures. One method of producing sterically hindered amines has included the catalytic tertiarybutylamination of triethylene glycol to produce bis-(tertiarybutylaminoethoxy) amine and ethoxyethanoltertiarybutylamine. However, this process has drawbacks because under CO2 rich conditions and/or high bis-(tertiarybutylaminoethoxy) ethane content, the amine salt can precipitate out of solution during the acid gas removal process and fouling of the equipment may occur. In addition, the costs associated with the starting reaction materials necessary to produce sterically hindered amines are generally high and prior art processes have generally yielded high levels of undesirable by-products, resulting in only 25-30% useable product.